1,1 -dialkoxy-2- -1 - alkene

An alcohol is oxidized with Fetizon s reagent in the presence of a very oxidation-sensitive dialkoxy alkene that, for instance, suffers selective cleavage with no reaction on the alcohol moiety on contact with PCC. 

Interestingly, both researches employed the same technique to install the methyl tetronate ring, that is, addition of the lithium anion of 4-methoxy-3-methyl-2(5H)-furanone to an aldehyde (106 or 113), but Kende used a TfjO-mediated dehydration to finish the synthesis, whereas Overman obtained the final structures after a Corey-Winter reaction to form the dialkoxy alkene unit (Scheme 1.16). In 2012, Martin et al. [77] managed to prepare enantioselectively Overman s intermediate 113 by an elegant cascade of reactions that culminates in the intramolecular dipolar cycloaddition of 119, prepared from 2-deoxy-D-ribose (120) (Scheme 1.16). 

Another important example is the addition of alkene oxides, say ethylene oxide, to compounds of the proton donor class such as amines, alcohols, water, and hydrazine to form monoalkoxy, dialkoxy, trialkoxy, etc., derivatives, some examples of which are shown below ... 

Dioxazolidines are produced by cyclization of A,A-dialkoxy- or A -alkoxy-A -chloroamines (Scheme 11) <93CRV725>. The synthetic potential of this method far surpasses that of the photochemical addition of nitrobenzene to alkenes <84CHEC-1(6)-914). 

Generell sind auch (jE )-2-Nitro-1-phenylthio-l-alkene einsetzbar, die unter Abspaltung der Phenylthio-Funktion zu l,1-Dialkoxy-2-nitro-alkanen (77-78%)4reagieren ... 

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